My tesponse to someone nonbinary is same as for cis, trans and anyone else. "Hello"
I got no issues with nonbinary, trans, or my fellow cishets or anyone LGBT. I do take issue with those that are only engaing in suppression and oppression of LGBT through willful ignorance, acting in bad faith, or any other reason.
TERFs sound like right wing descriptions of feminism. That's by design. Groups like LGB Alliance probably think fascists will spare them. They won't be. At best they won't be tortured but killed quickly. TERFs will either stab the useful idiots in the back or be asking why they were stabbed.